空話不多說，直接上代碼吧
體式格局一：Blob和FileReader 對象
完成道理：
- 運用xhr要求圖片,並設置返回的文件範例為Blob對象[xhr.responseType = “blob”]
- 運用FileReader 對象吸收blob
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>js 圖片轉base64體式格局</title>
</head>
<body>
<p id="container1"></p>
<script>
getBase64("https://z649319834.github.io/Learn_Example/video_track/webvtt.jpg")
function getBase64(imgUrl) {
window.URL = window.URL || window.webkitURL;
var xhr = new XMLHttpRequest();
xhr.open("get", imgUrl, true);
// 至關重要
xhr.responseType = "blob";
xhr.onload = function () {
if (this.status == 200) {
//獲得一個blob對象
var blob = this.response;
console.log("blob", blob)
// 至關重要
let oFileReader = new FileReader();
oFileReader.onloadend = function (e) {
let base64 = e.target.result;
console.log("體式格局一》》》》》》》》》", base64)
};
oFileReader.readAsDataURL(blob);
//====為了在頁面顯現圖片，能夠刪除====
var img = document.createElement("img");
img.onload = function (e) {
window.URL.revokeObjectURL(img.src); // 消滅開釋
};
let src = window.URL.createObjectURL(blob);
img.src = src
document.getElementById("container1").appendChild(img);
//====為了在頁面顯現圖片，能夠刪除====
}
}
xhr.send();
}
</script>
</body>
</html>
體式格局二：canvas.toDataURL()要領
完成道理：
- 運用canvas.toDataURL()要領
- 須要處置懲罰圖片跨域題目 image.crossOrigin = ”;
- 運用了Jquery庫的$.Deferred()要領
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>js 圖片轉base64體式格局</title>
</head>
<body>
<p id="container2"></p>
<script src="https://apps.bdimg.com/libs/jquery/2.1.1/jquery.min.js"></script>
<script>
let imgSrc = "https://z649319834.github.io/Learn_Example/video_track/webvtt.jpg";
//width、height調用時傳入詳細像素值，掌握大小 ,不傳則默許圖象大小
function getBase64Image(img, width, height) {
var canvas = document.createElement("canvas");
canvas.width = width ? width : img.width;
canvas.height = height ? height : img.height;
var ctx = canvas.getContext("2d");
ctx.drawImage(img, 0, 0, canvas.width, canvas.height);
var dataURL = canvas.toDataURL();
return dataURL;
}
function getCanvasBase64(img) {
var image = new Image();
//至關重要
image.crossOrigin = '';
image.src = img;
//至關重要
var deferred = $.Deferred();
if (img) {
image.onload = function () {
deferred.resolve(getBase64Image(image));//將base64傳給done上傳處置懲罰
document.getElementById("container2").appendChild(image);
}
return deferred.promise();//題目要讓onload完成后再return sessionStorage['imgTest']
}
}
getCanvasBase64(imgSrc)
.then(function (base64) {
console.log("體式格局二》》》》》》》》》",base64);
}, function (err) {
console.log(err);
});
</script>
</body>
</html>
